Wormhole Characterization Using NMR

In carbonate reservoirs, the mechanism of acidizing revolves around the development of wormholes. Therefore, understanding these wormholes is essential to increase their efficiency, and as a result, optimize the stimulation treatment. Characterization of wormholing efficiency using coreflooding data and computerized tomography (CT) scanning is widely known in the industry. In addition, computational fluid dynamics (CFD) have been used to model the flow in wormhole networks. Using Nuclear Magnetic Resonance (NMR) to study and characterize a full breakthrough-wormhole is still a new initiative. NMR, in general, provides fluid saturation by imaging the nuclide concentration of a variety of nuclei and the information about the pore structure and the fluid-rock interaction by measuring the longitudinal and transverse relaxation time, and diffusion constant of the nuclei of interest, mostly proton (1H). This set of information is translated into porosity values and distribution, and can be further processed to generate accurate permeability values. In this work, NMR analysis was successfully conducted on fully broken through core plugs. The results of NMR showed changes in the porosity and permeability. In addition, NMR detected a connectivity changes between the micro- and macropores. The acquired data from NMR was combined with CT and coreflooding data to further help to understand the properties of wormhole created.